冻融循环对泡沫沥青再生混合料微观结构的影响

为了探究泡沫沥青冷再生混合料抗水损害能力的衰变情况,选取6种不同级配泡沫沥青冷再生混合料,采用劈裂强度试验及电子断层扫描试验,系统研究了不同冻融循环次数下混合料强度衰减特性、空隙级配及最可几孔径的变化规律.结果表明:随着冻融循环的增加,冷再生混合料的强度明显减小,微空隙显著减小,大空隙显著增加,空隙数目的变化直接影响到混合料的强度.电子断层扫描试验及劈裂强度试验结果表明:在总空隙率相同的条件下,微空隙越多混合料强度越高;大空隙越多混合料强度越低.以此为基础提出再生混合料内部空隙的3种分类:无害孔、少害孔及有害孔.前2次冻融循环对冷再生混合料最可几孔径影响最大.在相同的冻融次数下初始空隙率越大泡沫沥青冷再生混合料的最可几孔径越大.

Impacts of Freeze-Thaw Cycles on Microscopic Characteristics of Recycled Mixture Using Foamed Asphalt

In order to explore decay rule of moisture damage resistance of cold recycled mixture using foamed asphalt, 6 kinds of gradation cold recycled mixture using foamed asphalt was selected to study strength characteristics. Meanwhile, the indirect tensile strength test and computerized tomography ( CT) test were conducted to analyze air voids gradation and the most probable air voids diameter under different freeze-thaw cycles. As the freeze-thaw cycle increased, the strength of the recycled mixture prominently reduced, the micro-void significantly decreased, while the large gap increased significantly. The CT and indirect tensile strength ( ITS) test results show that the more the micro-void is, the higher the strength when they have the same total air voids. The more the large volume voids is, the lower the strength of specimens . The division method of air voids which is in cold recycled mixture of using foamed asphalt was put forward. The first two freeze-thaw cycles of cold recycled mixture had significant influence. The larger the initial void volume is, the larger the most probable air void is.